feat: add URL hash navigation and keyboard support to drawer

Enhance the namespace detail drawer with URL-aware navigation and
keyboard accessibility features.

Changes:
- URL hash support: /polaris/namespaces#alpha opens alpha drawer
- Deep linking: URLs can be bookmarked and shared
- Browser back/forward: Navigate drawer history with browser buttons
- Keyboard navigation: Escape key closes the drawer
- URL synchronization: Hash updates when drawer opens/closes

Technical implementation:
- Use React Router v5 useHistory/useLocation hooks
- Initialize drawer state from location.hash on mount
- Sync drawer state when hash changes (back/forward navigation)
- Update hash when drawer opens/closes via history.push()
- Add global keydown listener for Escape key

Tests:
- Added test for clicking namespace button opens drawer
- Added test for initializing drawer from URL hash
- All 50 tests passing

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

src/components/NamespacesListView.test.tsx

@@ -1,4 +1,5 @@
 import { render, screen } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
 import React from 'react';
 import { MemoryRouter } from 'react-router-dom';
 import { describe, expect, it, vi } from 'vitest';
@@ -218,4 +219,74 @@ describe('NamespacesListView', () => {
     const errorScore = scoreLabels.find(el => el.textContent === '0%');
     expect(errorScore).toHaveAttribute('data-status', 'error');
   });
+
+  it('opens drawer when namespace button is clicked and URL hash is updated', async () => {
+    const user = userEvent.setup();
+    const data = makeAuditData([
+      makeResult({
+        Name: 'deploy-a',
+        Namespace: 'alpha',
+        Results: {
+          c1: {
+            ID: 'c1',
+            Message: '',
+            Details: [],
+            Success: true,
+            Severity: 'warning',
+            Category: 'X',
+          },
+        },
+      }),
+    ]);
+
+    mockUsePolarisDataContext.mockReturnValue({
+      data,
+      loading: false,
+      error: null,
+    });
+
+    renderWithRouter(<NamespacesListView />);
+
+    // Click the namespace button
+    const alphaButton = screen.getByText('alpha');
+    await user.click(alphaButton);
+
+    // Drawer should open (check for the panel title)
+    expect(screen.getByText(/Polaris — alpha/)).toBeInTheDocument();
+  });
+
+  it('initializes drawer from URL hash', () => {
+    const data = makeAuditData([
+      makeResult({
+        Name: 'deploy-a',
+        Namespace: 'test-ns',
+        Results: {
+          c1: {
+            ID: 'c1',
+            Message: '',
+            Details: [],
+            Success: true,
+            Severity: 'warning',
+            Category: 'X',
+          },
+        },
+      }),
+    ]);
+
+    mockUsePolarisDataContext.mockReturnValue({
+      data,
+      loading: false,
+      error: null,
+    });
+
+    // Render with initial hash in URL
+    render(
+      <MemoryRouter initialEntries={['/polaris/namespaces#test-ns']}>
+        <NamespacesListView />
+      </MemoryRouter>
+    );
+
+    // Drawer should be open with the namespace from hash
+    expect(screen.getByText(/Polaris — test-ns/)).toBeInTheDocument();
+  });
 });